I've recently installed a new serial link to a neighboring site to perform equal-cost load balancing with EIGRP.
However, my boss refuses to issue me another IP network for this link, and he forbids me to variably subnet the existing network. Can you make it work? The exiting IP for serial link is 192.168.12.0/24 topology.PNG
You installed a second serial link to another site (which I'm guessing costs money). But your boss (who I'm also guessing approved this new link) refuses to provide you with an IP address so that you can use the link? And he "forbids" you from variably subnetting the existing serial link IP address?
This smalls like a homework type scenario.
But what the heck: You're using private IP addresses. I can only assume that you know what addresses are currently in use (if not, look at the routing table). Then select an unused address. Maybe something like 192.168.255.0/30.